* Re: [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled [not found] ` <20210218231202.15426-1-peterx@redhat.com> @ 2021-03-10 7:48 ` Naresh Kamboju 2021-03-10 16:57 ` Peter Xu 0 siblings, 1 reply; 3+ messages in thread From: Naresh Kamboju @ 2021-03-10 7:48 UTC (permalink / raw) To: Peter Xu, Linux-Next Mailing List Cc: open list, linux-mm, Andrea Arcangeli, Axel Rasmussen, Mike Rapoport, Kirill A . Shutemov, Andrew Morton, Matthew Wilcox, Mike Kravetz, lkft-triage, Arnd Bergmann, Stephen Rothwell Hi Peter, On Fri, 19 Feb 2021 at 04:43, Peter Xu <peterx@redhat•com> wrote: > > Huge pmd sharing could bring problem to userfaultfd. The thing is that > userfaultfd is running its logic based on the special bits on page table > entries, however the huge pmd sharing could potentially share page table > entries for different address ranges. That could cause issues on either: > > - When sharing huge pmd page tables for an uffd write protected range, the > newly mapped huge pmd range will also be write protected unexpectedly, or, > > - When we try to write protect a range of huge pmd shared range, we'll first > do huge_pmd_unshare() in hugetlb_change_protection(), however that also > means the UFFDIO_WRITEPROTECT could be silently skipped for the shared > region, which could lead to data loss. > > Since at it, a few other things are done altogether: > > - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because > that's definitely something that arch code would like to use too > > - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when > trying to share huge pmd. Switch to the want_pmd_share() helper. > > Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share(). > > Reviewed-by: Mike Kravetz <mike.kravetz@oracle•com> > Reviewed-by: Axel Rasmussen <axelrasmussen@google•com> > Signed-off-by: Peter Xu <peterx@redhat•com> > --- > arch/arm64/mm/hugetlbpage.c | 3 +-- > include/linux/hugetlb.h | 2 ++ > include/linux/userfaultfd_k.h | 9 +++++++++ > mm/hugetlb.c | 20 ++++++++++++++------ > 4 files changed, 26 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > index 6e3bcffe2837..58987a98e179 100644 > --- a/arch/arm64/mm/hugetlbpage.c > +++ b/arch/arm64/mm/hugetlbpage.c > @@ -284,8 +284,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, > */ > ptep = pte_alloc_map(mm, pmdp, addr); > } else if (sz == PMD_SIZE) { > - if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && > - pud_none(READ_ONCE(*pudp))) > + if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp))) While building Linux next 20210310 tag for arm64 architecture with - CONFIG_ARM64_64K_PAGES=y enabled the build failed due to below errors / warnings make --silent --keep-going --jobs=8 O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- 'CC=sccache aarch64-linux-gnu-gcc' 'HOSTCC=sccache gcc' aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! aarch64-linux-gnu-ld: arch/arm64/mm/hugetlbpage.o: in function `huge_pte_alloc': hugetlbpage.c:(.text+0x7d8): undefined reference to `want_pmd_share' Reported-by: Naresh Kamboju <naresh.kamboju@linaro•org> Steps to reproduce: ---------------------------- # TuxMake is a command line tool and Python library that provides # portable and repeatable Linux kernel builds across a variety of # architectures, toolchains, kernel configurations, and make targets. # # TuxMake supports the concept of runtimes. # See https://docs.tuxmake.org/runtimes/, for that to work it requires # that you install podman or docker on your system. # # To install tuxmake on your system globally: # sudo pip3 install -U tuxmake # # See https://docs.tuxmake.org/ for complete documentation. tuxmake --runtime podman --target-arch arm64 --toolchain gcc-9 --kconfig defconfig --kconfig-add https://builds.tuxbuild.com/1pYCSoc1oGtPWlPgLAJxbHx07kL/config Build link, https://builds.tuxbuild.com/1pYCSoc1oGtPWlPgLAJxbHx07kL/ -- Linaro LKFT https://lkft.linaro.org ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled 2021-03-10 7:48 ` [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Naresh Kamboju @ 2021-03-10 16:57 ` Peter Xu 2021-03-10 18:09 ` Naresh Kamboju 0 siblings, 1 reply; 3+ messages in thread From: Peter Xu @ 2021-03-10 16:57 UTC (permalink / raw) To: Naresh Kamboju Cc: Linux-Next Mailing List, open list, linux-mm, Andrea Arcangeli, Axel Rasmussen, Mike Rapoport, Kirill A . Shutemov, Andrew Morton, Matthew Wilcox, Mike Kravetz, lkft-triage, Arnd Bergmann, Stephen Rothwell [-- Attachment #1: Type: text/plain, Size: 3289 bytes --] On Wed, Mar 10, 2021 at 01:18:42PM +0530, Naresh Kamboju wrote: > Hi Peter, Hi, Naresh, > > On Fri, 19 Feb 2021 at 04:43, Peter Xu <peterx@redhat•com> wrote: > > > > Huge pmd sharing could bring problem to userfaultfd. The thing is that > > userfaultfd is running its logic based on the special bits on page table > > entries, however the huge pmd sharing could potentially share page table > > entries for different address ranges. That could cause issues on either: > > > > - When sharing huge pmd page tables for an uffd write protected range, the > > newly mapped huge pmd range will also be write protected unexpectedly, or, > > > > - When we try to write protect a range of huge pmd shared range, we'll first > > do huge_pmd_unshare() in hugetlb_change_protection(), however that also > > means the UFFDIO_WRITEPROTECT could be silently skipped for the shared > > region, which could lead to data loss. > > > > Since at it, a few other things are done altogether: > > > > - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because > > that's definitely something that arch code would like to use too > > > > - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when > > trying to share huge pmd. Switch to the want_pmd_share() helper. > > > > Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share(). > > > > Reviewed-by: Mike Kravetz <mike.kravetz@oracle•com> > > Reviewed-by: Axel Rasmussen <axelrasmussen@google•com> > > Signed-off-by: Peter Xu <peterx@redhat•com> > > --- > > arch/arm64/mm/hugetlbpage.c | 3 +-- > > include/linux/hugetlb.h | 2 ++ > > include/linux/userfaultfd_k.h | 9 +++++++++ > > mm/hugetlb.c | 20 ++++++++++++++------ > > 4 files changed, 26 insertions(+), 8 deletions(-) > > > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > > index 6e3bcffe2837..58987a98e179 100644 > > --- a/arch/arm64/mm/hugetlbpage.c > > +++ b/arch/arm64/mm/hugetlbpage.c > > @@ -284,8 +284,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, > > */ > > ptep = pte_alloc_map(mm, pmdp, addr); > > } else if (sz == PMD_SIZE) { > > - if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && > > - pud_none(READ_ONCE(*pudp))) > > + if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp))) > > While building Linux next 20210310 tag for arm64 architecture with > > - CONFIG_ARM64_64K_PAGES=y > > enabled the build failed due to below errors / warnings > > make --silent --keep-going --jobs=8 > O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=arm64 > CROSS_COMPILE=aarch64-linux-gnu- 'CC=sccache aarch64-linux-gnu-gcc' > 'HOSTCC=sccache gcc' > aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! > aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! > aarch64-linux-gnu-ld: arch/arm64/mm/hugetlbpage.o: in function `huge_pte_alloc': > hugetlbpage.c:(.text+0x7d8): undefined reference to `want_pmd_share' > > Reported-by: Naresh Kamboju <naresh.kamboju@linaro•org> Sorry for the issue & thanks for the report. Would you please check whether the patch attached could fix the issue? -- Peter Xu [-- Attachment #2: 0001-mm-hugetlb-Fix-build-with-ARCH_WANT_HUGE_PMD_SHARE.patch --] [-- Type: text/plain, Size: 1671 bytes --] From 4072042b415d1f78ac1ab017671e345b414ca6ab Mon Sep 17 00:00:00 2001 From: Peter Xu <peterx@redhat•com> Date: Wed, 10 Mar 2021 11:48:56 -0500 Subject: [PATCH] mm/hugetlb: Fix build with !ARCH_WANT_HUGE_PMD_SHARE want_pmd_share() is undefined with !ARCH_WANT_HUGE_PMD_SHARE since it's put by accident into a "#ifdef ARCH_WANT_HUGE_PMD_SHARE" block. Moving it out won't work either since vma_shareable() is only defined within the block. Define it for !ARCH_WANT_HUGE_PMD_SHARE instead. Fixes: 5b109cc1cdcc ("hugetlb/userfaultfd: forbid huge pmd sharing when uffd enabled") Cc: Andrew Morton <akpm@linux-foundation•org> Cc: Mike Kravetz <mike.kravetz@oracle•com> Cc: Axel Rasmussen <axelrasmussen@google•com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro•org> Signed-off-by: Peter Xu <peterx@redhat•com> --- mm/hugetlb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index d58f1456fe27..8dda7e034477 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5469,9 +5469,6 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) { -#ifndef CONFIG_ARCH_WANT_HUGE_PMD_SHARE - return false; -#endif #ifdef CONFIG_USERFAULTFD if (uffd_disable_huge_pmd_share(vma)) return false; @@ -5616,6 +5613,11 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, unsigned long *start, unsigned long *end) { } + +bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) +{ + return false; +} #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB -- 2.26.2 ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled 2021-03-10 16:57 ` Peter Xu @ 2021-03-10 18:09 ` Naresh Kamboju 0 siblings, 0 replies; 3+ messages in thread From: Naresh Kamboju @ 2021-03-10 18:09 UTC (permalink / raw) To: Peter Xu Cc: Linux-Next Mailing List, open list, linux-mm, Andrea Arcangeli, Axel Rasmussen, Mike Rapoport, Kirill A . Shutemov, Andrew Morton, Matthew Wilcox, Mike Kravetz, lkft-triage, Arnd Bergmann, Stephen Rothwell On Wed, 10 Mar 2021 at 22:27, Peter Xu <peterx@redhat•com> wrote: > > On Wed, Mar 10, 2021 at 01:18:42PM +0530, Naresh Kamboju wrote: > > Hi Peter, > > Hi, Naresh, > > > > > On Fri, 19 Feb 2021 at 04:43, Peter Xu <peterx@redhat•com> wrote: > > > > > > Huge pmd sharing could bring problem to userfaultfd. The thing is that > > > userfaultfd is running its logic based on the special bits on page table > > > entries, however the huge pmd sharing could potentially share page table > > > entries for different address ranges. That could cause issues on either: > > > > > > - When sharing huge pmd page tables for an uffd write protected range, the > > > newly mapped huge pmd range will also be write protected unexpectedly, or, > > > > > > - When we try to write protect a range of huge pmd shared range, we'll first > > > do huge_pmd_unshare() in hugetlb_change_protection(), however that also > > > means the UFFDIO_WRITEPROTECT could be silently skipped for the shared > > > region, which could lead to data loss. > > > > > > Since at it, a few other things are done altogether: > > > > > > - Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because > > > that's definitely something that arch code would like to use too > > > > > > - ARM64 currently directly check against CONFIG_ARCH_WANT_HUGE_PMD_SHARE when > > > trying to share huge pmd. Switch to the want_pmd_share() helper. > > > > > > Since at it, move vma_shareable() from huge_pmd_share() into want_pmd_share(). > > > > > > Reviewed-by: Mike Kravetz <mike.kravetz@oracle•com> > > > Reviewed-by: Axel Rasmussen <axelrasmussen@google•com> > > > Signed-off-by: Peter Xu <peterx@redhat•com> > > > --- > > > arch/arm64/mm/hugetlbpage.c | 3 +-- > > > include/linux/hugetlb.h | 2 ++ > > > include/linux/userfaultfd_k.h | 9 +++++++++ > > > mm/hugetlb.c | 20 ++++++++++++++------ > > > 4 files changed, 26 insertions(+), 8 deletions(-) > > > > > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > > > index 6e3bcffe2837..58987a98e179 100644 > > > --- a/arch/arm64/mm/hugetlbpage.c > > > +++ b/arch/arm64/mm/hugetlbpage.c > > > @@ -284,8 +284,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, > > > */ > > > ptep = pte_alloc_map(mm, pmdp, addr); > > > } else if (sz == PMD_SIZE) { > > > - if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && > > > - pud_none(READ_ONCE(*pudp))) > > > + if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp))) > > > > While building Linux next 20210310 tag for arm64 architecture with > > > > - CONFIG_ARM64_64K_PAGES=y > > > > enabled the build failed due to below errors / warnings > > > > make --silent --keep-going --jobs=8 > > O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=arm64 > > CROSS_COMPILE=aarch64-linux-gnu- 'CC=sccache aarch64-linux-gnu-gcc' > > 'HOSTCC=sccache gcc' > > aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! > > aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! > > aarch64-linux-gnu-ld: arch/arm64/mm/hugetlbpage.o: in function `huge_pte_alloc': > > hugetlbpage.c:(.text+0x7d8): undefined reference to `want_pmd_share' > > > > Reported-by: Naresh Kamboju <naresh.kamboju@linaro•org> > > Sorry for the issue & thanks for the report. Would you please check whether > the patch attached could fix the issue? The attached patch build tested and build pass for arm64 including 64k pages config. CONFIG_ARM64_64K_PAGES=y - Naresh ^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-03-10 7:48 ` [PATCH v4 2/4] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Naresh Kamboju
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